Over the years, I have seen many dead trees and shrubs in new landscape projects, and the first thing that comes to mind is; were they planted correctly? Most of the time, I find that improper planting is the reason the plant didn't make it. So, here's some instruction on the correct way to plant a tree or shrub.
Start by digging a hole that is deep enough to cover the roots all the way to the bottom of the "trunk flare". The "trunk flare" is the part of the trunk that starts to widen just above the root top.
When the hole is the right depth, widen it to 3 times the diameter of the root ball, without digging the hole any deeper (roots grow out to the sides).
Now build a mound in the center of the hole large enough to spread the roots out over the top of. Pack it down so it won't sink in the future. Now set the plant over the mound of soil with the roots spread out over it. The hole should be wide enough so that none of the roots are cramped when you spread them out. They should easily be able to grow out sideways.
Done correctly, the tree should be sitting so that the trunk flare is sitting slightly above the top edge of the hole and the roots should be spread out like octopus legs over the mound you created.
Now backfill the hole enough to hold the tree or shrub in place. Fill the hole with water and let it soak in. When it's finished soaking in, fill the rest of the hole with soil. The trunk flare should be showing above the surface. If it looks like a telephone pole sticking out of the ground, you planted too deep.
If it all looks correct, lightly press the soil down around the base to squeeze out the air pockets, and water the tree or shrub thoroughly. Cover the area with 2" to 3" of mulch.
Make sure the new planting gets 5 gallons of water a week while it's getting established.
Note: Make sure that you keep the roots moist the whole time you have them exposed. Do not let them dry out.
If the tree is in an extremely windy spot, tether it on two sides for the first year. Make sure the tree still has a little room to sway.
For better results, plant in the fall when the plant has stop putting on top growth or in the early spring once the soil is workable.